Pouches made from films or laminates have found use in a variety of applications. For example, they are used in packaging food, medical or cleaning products to hold low viscosity fluids (e.g., juice and soda), high viscosity fluids (e.g., condiments and sauces), fluid/solid mixtures (e.g., soups and vegetables in brine), gels, powders, and powder materials.
The benefit of such pouches lies, at least in part, in the fact that, they are easy to store prior to filling and produce very little waste when discarded. The pouches can be formed into a variety of sizes and shapes, and can be filled under cold or hot conditions. In some cases the pouches have to withstand drastic thermal and/or chemical and/or physical treatments, such as pasteurization or sterilization, in order to reduce or eliminate bacterial contamination.
Pouches can be pre-made or, alternatively, they can be formed just before being filled, for example according to Vertical Form Fill Seal (VFFS) packaging systems that have proven to be very useful in packaging a wide variety of flowable products. The VFFS process is known to those of skilled in the art, and described for example in U.S. Pat. No. 4,589,247.
A flowable product is introduced through a central, vertical fill tube to a formed tubular film having been sealed transversely at its lower end, and longitudinally. The pouch is then completed by sealing the upper end of the tubular segment, and severing the pouch from the tubular film above it.
The choice of packaging materials is very important, and should be matched to the intended end use of the pouch.
Said materials should ideally show dimensional and seal stability (no deformation, pleats or bubbles when filled-in with hot fluids), easy sealability, heat and abuse resistance, good optical properties, chemical stability (no release of substances into the package) and, for certain applications, gas barrier characteristics.
There are several multilayer structures known in the art that have been used for these specific applications such as for example the five layered films described in EP0946360, comprising a core polyamide layer, two intermediate tie layers, disposed on opposite surfaces of the core layer, and two outer layers, each disposed on a surface of the respective intermediate layer, comprising an ethylene/alpha olefin copolymer) or the seven layered films disclosed in WO02074537, in which the polyamide core layer additionally comprises a gas barrier layer substantially made of ethylvinylalcohol copolymer (EVOH).
These known structures however are not fully satisfactory, especially as far as mechanical and optical properties are concerned.
We have now surprisingly found that by inserting at least one, preferably two additional HDPE layers into standard fluid products packaging structures, new multilayer films which overcome the drawbacks mentioned above are provided. The films of the present invention show a very good balance of mechanical, chemical and, optionally, barrier properties, good sealability, heat resistance and unexpectedly improved optical properties.